1. Field
With respect to the action of a plug-type coupling and molded sealing ring used therewith, reference is made to the older patent application DE 10 2004 019 800.4 of the same applicant's.
2. Description of the Related Art
As prior art, reference is also made to DE 24 13 750 C2, which also describes a molded sealing ring as a two-element sealing ring in FIG. 5.
A molded sealing ring of this type is used preferably for plug-type couplings, since low plug-in forces exist. With plug-type couplings, however, the problem exists that the groove in the plug is shaped relatively inexact and, moreover, only a shallow groove depth exists, since the entire plug is implemented as a drawn part and, therefore; has only a shallow groove depth. This would be different if the groove were produced by machining.
Due to the use of a plug that is implemented as a sheet metal part, the shortcoming arises that relatively wide tolerances exist in the region of the seal connection between the plug and socket, since—as explained above—the plug preferably consists of a sheet metal part and the socket may consist of various different materials, such as, e.g., plastic, diecasting, and other metal materials. Moreover, it may be implemented as a turned part or a drawn part.
Because of the associated short axial guide length when connecting the plug-type coupling, a large angle play accordingly results as well.
For the above reasons, the use of a lip seal according to the subject matter of the above-mentioned older patent application has proven successful on a large scale.
It has turned out now that in the case of pulsating stresses on the plug-type coupling, during which pulsations within a range of −200 mbar to +4 bar overpressure can occur, an extraordinarily high stress can occur for the seal connection. In addition to these pressure surges, an additive relative movement between the socket and the plug occurs as well, placing great demands on the lip seal.
In the case of the design according to DE 24 13 750, a lip seal will work only in combination with a highly precisely formed groove, since the two legs of the lip seal adjoin the flanks of the groove in a virtually form-fitting manner and no free spaces are created in this manner. A given pulsating stress therefore does not produce any lift-off effect or displacement effect of the static leg of the lip seal, as may be the case with the above-mentioned plug-type coupling.
In the case of a plug-type coupling comprising a lip-seal ring according to the subject matter of the older patent application, pulsating stresses lead to a so-called pumping effect. In the process, the lip seal shifts with its base leg against the rear groove flank, thus attaining a sealing effect between the base leg of the C-shaped contoured lip seal and the groove flank.
At the same time, however, the dynamic sealing lip also inflates, thus creating a pulling effect on the dynamic leg and the base leg, and a vacuum develops on the groove bottom, because the base leg is lifted out of the groove along with the static leg.
The medium is now suctioned from the pressurized side into the hollow space that has been created in this manner, because the static leg gives way and the back and the base leg seal too tightly on the circumferential annular sealing flank of the groove.
As soon as the pressure is removed from the pressure chamber, the lip seal is pushed forward in the direction against the pressure load, causing the sealing effect on the groove flanks to be reduced, and the medium is released from the negative-pressure carrying hollow space into the ambient space.
This describes the above-mentioned pumping effect, which is intended to be prevented with the inventive features described below.
The invention, therefore, has as its object to improve a plug-type coupling comprising a molded sealing ring of the above type in such a way that the above-described pumping effect is prevented.